1. Technical Field
The present invention relates to a fuel cell that directly converts chemical energy to electrical energy.
2. Background Art
Various types of fuel cells are known in the art. Among those, a molten carbonate type fuel cell comprises, as shown in FIG. 4 of the accompanying drawings, a plurality of fuel cell elements, each of which elements comprises an electrolyte plate (title) 1, and a cathode electrode (oxide electrode) 2 and an anode electrode (fuel electrode) 3. The title 1 is a molten carbonate-containing porous plate, and is interposed between the cathode and anode electrodes 2 and 3. The fuel cell elements are stacked via separators 4. Oxidizing gas OG is supplied to the cathode electrode 2 and fuel gas FG is supplied to the anode electrode 3, and power generation results from an electrical potential difference between the cathode 2 and the anode electrodes 3.
In the fuel cell, each title 1, cathode electrode 2 and anode electrode 2 generate heat respectively. Therefore, in order to secure proper functioning of the fuel cell, it is necessary to maintain the temperature of the tile 1 within a certain range, and to render the temperature distribution of the entire fuel cell as constant as possible.
In the conventional fuel cell, to this end, as shown in FIG. 5, the oxidizing gas OG and the fuel gas FG are supplied parallel to each other in the same direction in each cell element while being supplied in the opposite direction relative to the adjacent fuel cell elements. In other words, the fuel gas FG and the oxidizing gas OG that are respectively supplied into one fuel cell along the lower and the upper faces of the tile 1 flow in the same direction (upper two arrows FG and OG in FIG. 5), while the other pair of fuel gas FG and oxidizing gas OG (lower two arrows FG and OG in FIG. 5) supplied into the next fuel cell element flow in the opposite direction.
The reversal of the gas directions are believed effective in suppressing the maximum temperature of the electrolyte 1. However, as depicted in FIG. 6, the temperature at the exit is still high. In FIG. 6, a curve A represents a temperature of the cathode gas, B represents that of the anode gas, C represents that of the cell element, the vertical axis indicates temperature and the horizontal axis indicates a distance ratio from one end of the passage to the other end thereof, i.e,. 0 represents the entrance/exit and 1 the exit/entrance. On the other hand, the gas has to be hot at the entrance in order to ensure chemical reactions taking place afterwards. Referring to FIG. 4, preheated hot gas is supplied to the supple passage in order to ensure the reaction in the fuel cell element, and accordingly the hot gas is discharged into the discharge passage. High temperature gases make it impossible to use iron pipes in piping. The fuel cell also requires a preheating device for heating the gas to be supplied to the supply passage. The conventional fuel cell has these shortcomings since that exchange between a manifold portion of the fuel cell and the electrodes is out of concern in designating a fuel cell.